162 



♦ KNOWLEDGE ♦ 



[Sept. U, 1SS3. 



is not ^vanting. The external ear-opening is extremely 

 complicated, and its peculiarities are different in different 

 genera of owls. One kind even has the ear-opening on the 

 right side of a different shape from that on the left. Every- 

 body who has ever watched our English barn owl closely, 

 knows well that its sense of hearing is most keen and acute. 

 It is, doubtless, this large development of the exterior 

 sense-organs that makes the heads of most owls so dispro 

 portionately big. There is one peculiarity of the whole owl 

 group, however, which they share with a single other bird 

 of prey- — the osprey — and which does not seem immediately 

 connected in any way with their nocturnal habits, though 

 it fits in admirably with their usual skulking mode of life, 

 and that is, the power which they possess of reversing their 

 outer toe, so as to turn it outwards or inwards at will. A 

 peculiarity like this must probably descend to them 

 from a common ancestor, who perhaps was not yet 

 nocturnal in his mode of life. As a consequence, owls 

 can sit with two toes on one side of the perch and two on 

 the other, a thing impossible for hawks and eagles, whose 

 toes are arranged to go three on one side and one on the 

 other. 



Our own common barn, owl is a good representative of 

 the usual habits prevalent among the race at large ; but, 

 like most other successful groups, the owls have split up 

 into a good many genera and species, several of which 

 have diverged considerably in structure, and still more in 

 habits, from the central type. While most of them hunt 

 rats and mice, and such small deer, the great eagle-owl of 

 Germany and Switzerland eats not only rabbits, hares, 

 capercailzie, and pheasants, but even so large an animal 

 as the fawn of the roebuck. Other owls, again, have 

 taken to fishing, like their distant relative, the osprey ; 

 and, like him, they have lost the feathers on the lower 

 part of the leg, and acquired a series of small spikes on 

 the sole of the toes, to aid them in holding their slippery 

 prey. One of these is common in India, and three rarer 

 kinds frequent the streams and inland lakes of Africa. 

 A few owls have even reverted once more to the habit of 

 hunting their food by day, like the snowy owl, which is 

 perhaps the handsomest member of the entire race. Some 

 of the tiny continental species have greatly degenerated in 

 size, till they have grown no bigger than an ordinary 

 robin. Such decrease of size, though it looks at first sight 

 like a disadvantage, may really help a species in the 

 struggle for existence by enabling it to procure smaller but 

 more abundant food. The wee pigmy-owlet of the Mediter- 

 iranean region could easily pick up a livelihood for himself 

 in many districts where the great eagle-owl, adapted to 

 broad, forest-clad plains, would starve hopelessly. 



Herbert Spexcer — "The work which Herbert Spencer 

 has done in organizing the different departments of human 

 knowledge, so as to present the widest generalizations of 

 all the sciences in a new and wonderful light, as flowing 

 out of still deeper and wider truths concerning the uni- 

 verse as a whole ; the great number of profound generaliza- 

 tions which he has established incidentally to the pursuit 

 of this main object ; the endless rich and suggestive 

 thoughts which he has thrown out in such profusion by 

 the wayside along the course of this great philosophical 

 enterprise, — all this work is so manifest that none can fail 

 to recognise it. It is work of the calibre of th'at which 

 Aristotle and Newton did, though, coming in this latter 

 age, it as far surpasses their work in its vastness of per- 

 formance as the railway surpasses the sedan-chair, or as the 

 telegraph surpasses the carrier-pigeon." — Johx Fiske. 



PLEASANT HOURS WITH THE 

 MICROSCOPE. 



By Hesky J. Slack, F.C.S., F.R.M.S. 



EVERYBODY knows that in the middle of an ordinary 

 flower, say a geranium or a lily, there rises a column, 

 usually slender, with a peculiar formation at the top. In 

 the scarlet geranium this is five-fingered, in the lilies more 

 knobby and with three divisions. The column is the style 

 and the organ at the top the stigma. The two constitute 

 the pistil. In a perfect flower the observer will notice a 

 series of whorls, forming the calyx, the corolla, a group of 

 filaments bearing anthers and surrounding the pistil, and, 

 lastly, the pistil itself, more or less elongated, but in all 

 cases rising from the simple of compound ovary. It is very 

 interesting to notice the shape of these parts in various 

 flowers. There is great variety in the anthers and in the 

 stigmas, but the function of the former is always to pro- 

 duce the pollen or male element, and the stigma is adapted 

 to receive it, and cause it to convey some of its contents 

 to the ovules in the ovary. 



Pollen is of various sizes and shapes — frequently round 

 and frequently oval, or shuttle-shaped. In the melon it is 

 round and spiked like a horse-chestnut, and provided with 

 circular lids at certain spots. The passion - flower {P. 

 ccervlea) has round pollen, covered with a network pattern, 

 and provided with large lids. The musk plant, chicory, 

 mallow, and many others exhibit interesting varieties of 

 shape, and the " Micrographic Dictionary," pi. 32, gives a 

 figure of the pollen of Basella alba like a square box, with 

 the appearance of a roimd hole in the middle of each side. 

 Many sorts of pollen look iinder the microscope as if they 

 had holes in them, or slits, but these appearances probably 

 in all cases arise from those parts being thinner or more 

 transparent than the rest. When the pollen sprouts it is 

 from these spots, and in those which have lids the out- 

 growth forces them open. 



The stigma is provided with several means of holding the 

 pollen conveyed to it. It is roughened with glandular 

 papilla- in the scarlet geranium, and in many plants when 

 it is ready for the pollen it pours out a glutinous secretion. 

 It would lead us away from our present object to describe 

 the various contrivances by which plants avoid self-ferti- 

 lisation, and the different waj-s, by insect help and other- 

 wise, through which they receive pollen from other indi- 

 viduals. Let us suppose a pollen cell deposited upon a 

 stigma. It finds itself stimulated to put forth a slender 

 outgrowth, which has to work its way down the style and 

 reach the ovule it is intended to fertilise. Some plants 

 (gourds for example) enable this process to be traced, but 

 only skilled observers and dissectors are likely to see much. 

 Plants of the lily family offer the easiest means of seeing 

 the growth of pollen tubes. A little pollen should be 

 placed on a glass slide in a drop of the fluid secreted by 

 the stigma, lightly covered with thin glass, and steadily 

 watched. Lilium excelsum — the pretty, sweet-scented, 

 buff lily — and Z. Auratum are recommended. The sketches 

 given with this paper repre.^ent what occurred with the 

 pollen of a very beautiful plant now frequently found in 

 conservatories, and belonging to the Ginger family. It is 

 called Iledychium Gardnerianum. A fine specimen in full 

 flower is a splendid sight. The one in question exhibited 

 a broad head of flowers nearly a foot high. Each corolla 

 consists of six segments in two rows, the sixth being the 

 biggest, with a notched lip. The arrangement of the 

 anther and style is shown in Fig. D. The two lobes of the 

 anther clasp the style and lower part of the stigma, which 

 rises above them. The filament bearirs the anthrr i"; 



